In order to analyze the causes of cubitus varus deformity after fracture-separation of distal humeral epiphysis, we reviewed the change of carrying angle, and configuration of the distal humerus in 12 young children treated from January 1995 to July 1997. All of the patients were under the 3 years of age at the time of injury. Two types of Salter-Harris physeal injury could be seen: one is type I with slice fragment and the other is type II with large fragment. We could observe posteromedial displacement in all cases. The study group was classified into two groups according to the method of treatment such as, closed reduction with cast, and closed reduction with percutaneous pinning. Follow-up period averaged 18 months (from 12 months to 36 months). Configuration of distal humerus, including avascular necrosis and the change of carrying angle, were compared to the uninjured side. Cubitus varus deformity, which was encountered in 7 cases, were combined with the avascular necrosis of trochlea. The methods of treatment, age of injury, and the type of epiphyseal injury had no relationship with the development of cubitus varus. However, the avascular necrosis of trochlea had a relationship with the cubitus varus deformity, whatever the cause is. The fracture-separation of distal humeral epiphysis in young children is a rare injury, but is apt to produce cubitus varus deformity with development of the avascular necrosis of trochlea.